Method, system and apparatus for providing access mode selection to multimode terminal

ABSTRACT

A method, system and apparatus for providing access mode selection to multimode terminal are disclosed. After selecting an access mode according to a certain policy, a routing decision entity correspondingly instructs a routing execution entity to perform a call connection in the selected access mode. The method for providing access mode selection to multimode terminal includes the following steps: (1) when establishing a registration connection, a terminal notifies related information of a current access network type to a network side; and (2) when performing a call connection to a called party, a routing decision entity on the network side selects the access mode and correspondingly instructs a routing execution entity to perform the call connection according to the related information and the selected access mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/419,797, filed Apr. 7, 2009, which is a continuation of InternationalPatent Application No. PCT/CN2007/002929, filed Oct. 11, 2007. TheInternational Patent Application claims priority to Chinese PatentApplication No. 200610141098.8, filed on Oct. 12, 2006, and ChinesePatent Application No. 200710093787.0, filed Apr. 18, 2007. Theafore-mentioned patent applications are hereby incorporated by referencein their entirety.

FIELD OF THE INVENTION

The present invention relates to a communication field, and moreparticularly to a method, a system, and an apparatus for providingaccess mode selection to multimode terminal.

BACKGROUND

IP multimedia sub-system (IMS) is the IP multimedia sub-system inwideband code division multiple access (WCDMA) network defined by the3^(rd) generation partner project (3GPP) R5/R6 standard, and is a targetnetwork implementing packet voice and packet data of the 3G mobilenetwork and providing unified multimedia service and application. TheIMS adopts the IP packet domain as a bearing channel for controllingmessages and media transmission, and adopts the session initiationprotocol (SIP) as the call controlling message. In the IMS, the usersubscription data of the IMS is gathered and managed in a homesubscriber server (HSS), the service is uniformly provided by anapplication server (AS), and the session control is achieved by aserving-call session control function (S-CSCF), and the HSS, the AS andthe S-CSCF are completely separated in the network structure. Theservice is triggered to the AS via the S-CSCF, and a plurality of ASsmay cooperate with one another. The user gets access to the IMS via thecurrent local agent node—proxy-call session control function (P-CSCF),the session and the service control are achieved by a home domainservice node of the registration location, so that the user may obtainthe same service at different access points so as to separate theservice management, the session control and the bearing access, and toprovide services not related to the access and the location.

As a terminal supporting multi-access mode comes forth, the multimodeterminal of the user may register on the network via a plurality ofaccess domains, and user identities registering at the same time may bethe same or have a certain association (for the identities without theassociation, the process is the same as that of the single-modeterminal). Here, the referred multimode terminal includes, but notlimited to, the multimode terminal of the WCDMA, the multimode terminalof the CDMA2000, or the mobile multimode terminal of other standards.The user may initiate or receive the call at any registration domain, oreven may initiate or receive the call simultaneously at a plurality ofdomains.

It is a topic being researched by the 3GPP that which access network isselected by the network to be connected to the call when the multimodeterminal serves as a called party. Recently, the solution proposed bythe 3GPP is that an entity called as a domain selection function (DSF)is added into the IMS network. When receiving the call required to beconnected to the multimode terminal, the DSF entity makes an accessdomain selection decision according to various factors such as theoperator policy, the user preference, the terminal registration statusand various elements, and connects the call to the selected accessdomain according to a decision result. When the DSF selects to performthe call connection in a circuit switched (CS) domain, the DSF returns aCS domain access number to the S-CSCF so as to instruct the call to beconnected to the CS domain. When the DSF selects to perform the callconnection in the IMS domain, the DSF returns an IMS public useridentity (IMPU) of the user to the S-CSCF so as to instruct the call tobe connected at the IMS domain.

During the invention process, the inventor finds that a plurality ofaccess modes exists under a certain access domain, but in existingsystems, the problem of performing the access mode selection and thecall connection instruction by the network when the multimode terminalserves as the called party cannot be solved. That is, after selectingthe access mode according to a certain policy, the routing decisionentity cannot correspondingly instruct a routing execution entity toperform the call connection in the selected access mode.

SUMMARY

The present invention is directed to a method, a system, and anapparatus for providing access mode selection to multimode terminal, sothat after selecting an access mode according to a certain policy, arouting decision entity can instruct correspondingly a routing executionentity to perform a call connection in the selected access mode.

The present invention provides a method for providing access modeselection to multimode terminal, which includes the following steps: (1)when establishing a registration connection, a terminal notifies relatedinformation of a current access network type to a network side; and (2)when performing the call connection to a called party, a routingdecision entity on the network side selects the access mode andcorrespondingly instructs a routing execution entity to perform a callconnection according to the related information and the selected accessmode.

The present invention provides a system for providing access modeselection to multimode terminal, which includes: a multimode terminal,adapted to notify related information of a current access network typeto a network side when establishing a registration connection; a routingdecision entity, adapted to select the access mode and correspondinglytransmit a corresponding instruction according to the relatedinformation and the selected access mode when performing the callconnection to a called party; and a routing execution entity, adapted toperform the call connection according to the received instruction.

The present invention provides a routing decision entity, whichincludes: a saving unit, adapted to save an access network type identitycarried in a registration signaling; and an instructing unit, adapted toextract the corresponding access network type identity from the savingunit, after the routing decision entity selects an access mode accordingto a policy, and carry the extracted access network type identity in aninstruction signaling delivered to a routing execution entity.

The present invention provides a multimode terminal, which includes: anaccess network identifying unit, adapted to identify an adopted accessnetwork when a multimode terminal gets access to network; and an addingunit, adapted to add a corresponding access network type identity to aregistration signaling transmitted to a network side according to thecurrent access network of the multimode terminal identified by theaccess network identifying unit, when the multimode terminal initiatesto register.

The present invention further provides a routing decision entity, whichincludes: an associating unit, adapted to associate an access mode typenotified by a multimode terminal with a globally routable user agent(UA) uniform resource identifier (URI) (GRUU) distributed by a routingexecution entity; an access mode selection unit, adapted to select theaccess mode; and an instructing unit, adapted to acquire the GRUUcorresponding to the access mode type selected by the access modeselection unit from the associating unit, and instruct the routingexecution entity to perform a call connection with the GRUU.

The present invention further provides a multimode terminal, whichincludes: an identifying unit, adapted to identify an access mode typeof the multimode terminal when establishing a registration connection;and an adding unit, adapted to add the current access mode type of themultimode terminal identified by the identifying unit and a resourcename bound with the current access mode type to a registration messagetransmitted to a network side.

The present invention further provides a routing decision entity, whichincludes: a saving unit, adapted to save identification information of acurrent access network type notified by a terminal when establishing aregistration connection; a dividing unit, adapted to divide a callingsession message into media streams according to media components andtransmit a divided result; an access mode selection unit, adapted torespectively select an access mode corresponding to each media streamaccording to the divided result transmitted from the dividing unit; andan instructing unit, adapted to respectively acquire the identificationinformation corresponding to an access mode type selected by the accessmode selection unit for each media stream from the saving unit, andinstruct a routing execution entity to perform the media streamconnection with the identification information.

With the method for providing access mode selection to multimodeterminal, the system, and the apparatus according to the presentinvention, when establishing the registration connection, the terminalnotifies the related information of the current access network type tothe network side. In this manner, when performing the call connection tothe called party, the routing decision entity on the network sideselects the access mode and correspondingly instructs the routingexecution entity to perform the call connection according to the relatedinformation and the selected access mode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of steps of a method according to an embodimentof the present invention;

FIG. 2 is a flow chart of steps of a method according to a firstembodiment of the present invention;

FIG. 3 is a flow chart of signaling of a method according to a secondembodiment of the present invention;

FIG. 4 is a flow chart of signaling of a method according to a thirdembodiment of the present invention;

FIG. 5 is a flow chart of signaling of a method according to a fourthembodiment of the present invention;

FIG. 6 is a schematic structural view of a system according to a firstembodiment of the present invention;

FIG. 7 is a schematic modular view of the system according to the firstembodiment of the present invention;

FIG. 8 is a flow chart of steps of a method according to a fifthembodiment of the present invention;

FIG. 9 is a schematic structural view of a routing decision entityaccording to an embodiment of the present invention;

FIG. 10 is a schematic structural view of a multimode terminal accordingto an embodiment of the present invention;

FIG. 11 is a flow chart of signaling of a method according to a sixthembodiment of the present invention;

FIG. 12 is a flow chart of signaling of a method according to a seventhembodiment of the present invention;

FIG. 13 is a schematic structural view of another routing decisionentity according to an embodiment of the present invention; and

FIG. 14 is a flow chart of signaling of a method according to a ninthembodiment of the present invention.

DETAILED DESCRIPTION

After selecting an access mode according to a certain policy, a routingdecision entity correspondingly instructs a routing execution entity toperform a call connection in the selected access mode.

The present invention provides a method for providing access modeselection to multimode terminal, referring to FIG. 1, the method mainlyincludes the steps as follows.

In Step S1, when establishing a registration connection, a terminalnotifies related information of a current access network type to anetwork side.

In Step S2, when performing a call connection to a called party, arouting decision entity on the network side selects the access mode andcorrespondingly instructs a routing execution entity to perform the callconnection according to the related information and the selected accessmode.

The present invention further provides a system for providing accessmode selection to multimode terminal, which includes a multimodeterminal, a routing decision entity, and a routing execution entity. Themultimode terminal is adapted to notify related information of a currentaccess network type to a network side when establishing a registrationconnection. The routing decision entity is adapted to select the accessmode and correspondingly transmit a corresponding instruction accordingto the related information and the selected access mode when performingthe call connection to a called party. The routing execution entity isadapted to perform the call connection according to the receivedinstruction.

The method and the system according to the embodiments of the presentinvention are described in detail as follows.

In order to achieve that when the multimode terminal serves as a calledparty, after selecting the access mode, the routing decision entitycorrespondingly instructs the routing execution entity to perform thecall connection in the selected access mode, that is, the multimodeterminal may get access to an IMS domain via different access networksat the same time, when the user serves as the called party, the networkmay select a certain access network to perform the call connectionaccording to a policy, and when the user has a plurality of terminalssharing the IMPU on the access network, a forking operation of thenetwork is not affected. Referring to FIG. 2, the method according to afirst embodiment of the present invention includes the main steps asfollows.

In Step S101, when registering, the terminal notifies an access networktype identity to the network side.

In a reg-id solution, that is, when the user has only one terminal usinga certain IMPU, the network identifies a certain contact address byexpanding a usage scope of the reg-id to enable the reg-id to occur inthe call signaling, or designates one of the access types of themultimode terminal by directly designating one contact address. However,when the user has a plurality of terminals sharing the IMPU, and aplurality of terminals sharing the IMPU under the same access networkregisters on the IMS network, the DSF can only select one access networktype instead of a certain specific contact address, but the reg-idcannot be adapted to identify the different access network types, sounder the situation of selecting one access network, the DSF cannotinstruct the selected access network type to the S-CSCF with the reg-idto enable the S-CSCF to perform the forking operation on the pluralityof terminals registering on the access network. In the presentinvention, an identity capable of instructing the access network type isadded in the reg-id solution.

In the present invention, when registering, the terminal carries anaccess network type identity corresponding to the current access mode ina registration signaling, so that the routing decision entity on thenetwork side (may be, but not limited to, the DSF, or another AS) andthe routing execution entity (may be the S-CSCF) respectively acquireand save the access network type identity.

The manner of carrying the access network type identity in theregistration signaling includes, but not limited to, the three types asfollows:

In a first manner, a parameter is added after a contact header field soas to carry the access network type identity.

The access network type identity may be a new feature tag type, adaptedto identify the access network type corresponding to one specificcontact address. For example, a parameter accesstype=“wlan” is addedafter the contact header field to identify that the registration of thistime is performed via a wireless local area network (WLAN) accessnetwork. The parameter, together with other feature tags, is acquired bythe S-CSCF and the DSF during registration.

In a second manner, a parameter is added after the IMPU so as to carrythe access network type identity.

For the access network type identity, a parameter is added after theIMPU to represent the access network type, for example, a parameteraccesstype=“wlan” is added after the IMPU zhangsan@public.id to identifythe WLAN access network. The parameter, together with the IMPU, isacquired by the S-CSCF and the DSF during registration of the user.

In a third manner, a prefix or suffix is added to the IMPU so as tocarry the access network type identity.

The access network type identity may serve as the suffix or prefix ofthe IMPU, that is, the IMPU is expanded by adopting the suffix orprefix, and the access network type is identified in the suffix orprefix. For example, the IMPU is originally zhangsan@public.id, when theterminal gets access via the WLAN, the IMPU is expanded tozhangsan_wlan@public.id, and when the terminal gets access via the WCDM,the IMPU is expanded to zhangsan_utran@public.id. If the user has aplurality of terminals capable of getting access to the IMS network viathe WLAN, the terminals expand the IMPU of the terminals tozhangsan_wlan@public.id when registering.

In Step S102, when performing the call connection to the called party,the routing decision entity selects the access mode and correspondinglyinstructs, with the corresponding access network type identity, therouting execution entity.

When the user serves as the called party, after selecting one accessnetwork type according to various policies, the routing decision entity(may be the DSF) notifies the selected result to the routing executionentity (may be the S-CSCF) by carrying the corresponding access networktype identity in a call signaling returned to the S-CSCF.

The manners of carrying the corresponding access network type identityin the call signaling correspond to the three manners in Step S1.

Corresponding to the first manner in Step S101, when performing theconnection to the called party, after selecting one access network, theDSF notifies the selected access network type to the S-CSCF with acalling party preference mechanism, adds an Accept-contact header fieldto a session request message transmitted to the S-CSCF. The header fieldinstructs to use the certain specific access network type to perform thecall connection, for example, for Accept-Contact: *;accesstype=“wlan”,the format represents that the network should select the registrationconnection with the access network type being WLAN to perform the callconnection.

Corresponding to the second manner in Step S101, when performing theconnection to the called party, after selecting one access network, theDSF carries the newly added parameter behind the called party identity(IMPU) so as to notify the selected result to the S-CSCF. As comparedwith the first manner, the advantage of this manner is that the routingis directly performed with the called party identity instead of thecalling party preference mechanism, and the disadvantage is that the SIPparameter should be additionally added.

Corresponding to the third manner in Step S101, when the received calledparty identity is an original IMPU call, the DSF selects one accessnetwork, and then fills the called party identity as the expanded IMPUwith the added corresponding suffix or prefix in the call signalingtransmitted to the S-CSCF. In this manner, the S-CSCF may acquire theselected result of the DSF, and searches for the registration connectionperformed with the expanded IMPU. As compared with the second manner,the advantage of this manner is that it is not necessary to expand theparameter, and the routing is directly performed with the IMPU, and thedisadvantage is that other ASs not required acquiring the differentaccess network types of the terminal need to identify the IMPU.

In Step S103, the routing execution entity performs the call connectionin the access mode selected by the routing decision entity.

After acquiring the access network type identity carried in the callsignaling, the S-CSCF may search for which terminals of the user gettingaccess to the IMS domain under the access network (that is, whichterminals registering under the access network). If only one terminal isfound, the S-CSCF directly performs the call connection on the terminal,and if a plurality of terminals is found, the S-CSCF may perform theforking operation according to other policies.

Further, in order to solve the problem that the same terminal holds aplurality of registration connections at the IMS network, and theproblem that after selecting the access mode, the routing decisionentity cannot correspondingly instruct the routing execution entity toperform the call connection in the selected access mode, in the methodaccording to the embodiment of the present invention, when the terminalregisters, the network side identifies a plurality of registrationevents of the same terminal according to the acquired access networktype identity so as to hold the plurality of registration connections ofthe same terminal, so that the reg-id solution is not required.

The specific method is described as follow. When receiving theregistration signaling transmitted from the same terminal, the S-CSCFmay differentiate the registration signaling according to the accessnetwork type identities carried in the registration signaling. If theaccess network types of two registrations are the same, the originalregistration connection may be deregistered. If the access network typesof two registrations are different, it may be considered that a multipleregistration event exists, and the original registration connection isnot deregistered.

If the terminal needs to only register the latest access after changingthe access network, and the original access is not reserved, theterminal may initiate the deregistration to the original registration.If the terminal loses the original access network connection, and cannotinitiate the deregistration to the original registration, the networkmay judge whether to deregister the original connection according to thetwo continuous access network types. If the two continuous accessnetworks cannot coexist, for example, long term evolution (LTE) andglobal system for mobile communication radio access network (GERAN), thenetwork may deregister the original registration connection.Alternatively, the network may also not actively judge the accessnetwork type, but waits for timeout of the registration connection, andderegisters the original registration connection.

The method of the present invention is further described in detail withthree embodiments as follows.

In the method according to a second embodiment, one feature tag is addedto identify the access network type. It is assumed that the name of theadded feature tag is accesstype, with specific values including “wlan”,“lte”, “utran”, “geran”, and “hrpd” etc., for identifying variousdifferent access network types. Referring to FIG. 3, the method includesthe specific steps as follows.

In Step 1, the multimode terminal gets access to the IMS network via theWCDMA and initiates a registration request REGISTER, a contact-1 addressis carried in the request message, the accesstype parameter identifyingthe access network type is carried behind the contact header field, andthe value of the parameter is “utran”, representing that the multimodeterminal gets access to the IMS network via the WCDMA network. Afterbeing forwarded through other entities, the request message reaches theS-CSCF, and the process thereof is irrelevant to the present invention,so it is omitted here.

In Step 2, after the user finishes the registration process, the S-CSCFnotifies the user registration event and the contact content to the DSF(the DSF has subscribed the user registration event from the S-CSCFbefore, so here the S-CSCF may notify the DSF, and the subscriptionprocess is irrelevant to the present invention, so it is omitted here).

In Step 3, the multimode terminal gets access to the IMS network fromthe WLAN and initiates another registration request. The new contactaddress and the accesstype parameter with the value being “wlan” arecarried in the request message, representing that the multimode terminalgets access to the IMS network from the WLAN network again. Afterreceiving the registration message, the S-CSCF judges that this is amultiple registration initiated by the same terminal according to thedifferent access network type parameters, and the original contact-1connection is not deregistered. The S-CSCF acquires that this is amultiple registration event initiated by the same terminal in othermanners, for example, the reg-id according to a first technical solutionin the existing systems described herein.

In Step 4, the S-CSCF also notifies the new registration event of theuser to the DSF.

In Step 5, when one call is required to be connected to the user, thecall signaling INVITE is firstly transmitted to the S-CSCF.

In Step 6, the S-CSCF triggers the call signaling to the DSF withinitial filter criteria (iFC).

In Step 7, when deciding that it is necessary to be connected to thecall from the WLAN according to various policies, the DSF fills thecontent of the Accept-contact header field content withaccesstype=“wlan”, and returns the INVITE request with the header fieldto the S-CSCF.

In Step 8, according to the selection of the DSF, the S-CSCF selects theregistration connection with the accesstype being “wlan.” In thisembodiment, it is assumed that only one registration connection, thatis, contact-2, exists, the S-CSCF fills the Request-URI with the contentof the contact-2, and then delivers the INVITE request. In this manner,the call is connected with the WLAN access network. If a plurality ofregistration connections with the accesstype being “wlan” exists, theS-CSCF may deliver the call request to the connections at the same timeor in sequence, and performs the forking operation.

In Step 9, the multimode terminal receives the call under the WLAN andreturns the call final response.

In the method according to a third embodiment, the parameter is addedbehind the IMPU to identify the different access network types. The nameof the added parameter is accesstype, with specific values including“wlan”, “lte”, “utran”, “geran”, and “hrpd” etc., for identifyingvarious different access network types. Referring to FIG. 4, the methodincludes the specific steps as follows.

In Step 1, the multimode terminal gets access to the IMS network via theWCDMA and initiates a registration request REGISTER, a contact-1 addressis carried in the request message, the accesstype parameter identifyingthe access network type is carried behind the IMPU carried in the TOheader field, and the value of the parameter is “utran”, representingthat the multimode terminal gets access to the IMS network via the WCDMAnetwork. After being forwarded through other entities, the requestmessage reaches the S-CSCF, and the process is irrelevant to the presentinvention, so it is omitted here.

In Step 2, after the user finishes the registration process, the S-CSCFnotifies the user registration event, the registration user identityIMPU, and the contact content to the DSF (the DSF has subscribed theuser registration event from the S-CSCF before, so here the S-CSCF maynotify the DSF, and the subscription process is irrelevant to thepresent invention, so it is omitted here).

In Step 3, the multimode terminal gets access to the IMS network via theWLAN and initiates another registration request. The new contact addressand the accesstype parameter with the value being “wlan” behind the IMPUin the TO header field are carried in the request message, representingthat the multimode terminal gets access to the IMS network from the WLANnetwork again. After receiving the registration message, the S-CSCFjudges that this is a multiple registration initiated by the sameterminal according to the different access network type parameters, andthe original contact-1 connection is not deregistered. The S-CSCFacquires that this is the multiple registration event initiated by thesame terminal with other manners, for example, the reg-id according to afirst technical solution in the existing systems described herein.

In Step 4, the S-CSCF also notifies the new registration event of theuser to the DSF.

In Step 5, when one call is required to be connected to the user, thecall signaling INVITE is firstly transmitted to the S-CSCF.

In Step 6, the S-CSCF triggers the call signaling to the DSF via an iFC.

In Step 7, when deciding that it is necessary to be connected to thecall from the WLAN according to various policies, the DSF fills thecontent of the Request-URI header field content with accesstype=“wlan”to represent the selected result, and returns the INVITE request to theS-CSCF.

In Step 8, according to the selection of the DSF, the S-CSCF selects theregistration connection performed with the IMPU with accesstype being“wlan.” In this embodiment, it is assumed that only one registrationconnection, that is, contact-2, exists, the S-CSCF fills the Request-URIwith the content of the contact-2, and then delivers the INVITE request.In this manner, the call is connected with the WLAN access network. If aplurality of registration connections performed with the IMPU with theaccesstype parameter being “wlan” exists, the S-CSCF may deliver thecall request to the connections at the same time or in sequence, andperforms the forking operation.

In Step 9, the multimode terminal receives the call under the WLAN andreturns the call final response.

In the method according to a fourth embodiment, the IMPU is expanded,and the suffix is added behind the IMPU to identify the different accessnetwork types. Referring to FIG. 5, the method includes the specificsteps as follows:

In Step 1, the multimode terminal gets access to the IMS network via theWCDMA and initiates a registration request REGISTER, a contact-1 addressis carried in the request message, and a suffix_utran identifying theaccess network type is carried behind the IMPU carried in the TO headerfield, representing that the multimode terminal gets access to the IMSnetwork from the WCDMA network. After being forwarded with otherentities, the request message reaches the S-CSCF, and the process isirrelevant to the present invention, so it is omitted here.

In Step 2, after the user finishes the registration process, the S-CSCFnotifies the user registration event, the registration user identityIMPU, and the contact content to the DSF (the DSF has subscribed theuser registration event from the S-CSCF before, so here the S-CSCF maynotify the DSF, and the subscription process is irrelevant to thepresent invention, so it is omitted here).

In Step 3, the multimode terminal gets access to the IMS network fromthe WLAN and initiates another registration request, the new contactaddress and the suffix_utran after the IMPU carried in the TO headerfield are carried in the request message, representing that themultimode terminal gets access to the IMS network from the WLAN networkagain. After receiving the registration message, the S-CSCF judges thatthis is a multiple registration initiated by the same terminal accordingto the different access network type parameters, and the originalcontact-1 connection is not deregistered. The S-CSCF acquires that thisis the multiple registration event initiated by the same terminal withother manners, for example, the reg-id described in the existingsystems.

In Step 4, the S-CSCF also notifies the new registration event of theuser to the DSF.

In Step 5, when one call is required to be connected to the user, thecall signaling INVITE is firstly transmitted to the S-CSCF.

In Step 6, the S-CSCF triggers the call signaling to the DSF with aniFC.

In Step 7, when deciding that it is necessary to be connected to thecall from the WLAN according to various policies, the DSF modifies theRequest-URI requested by the INVITE to the expanded IMPU with the addedsuffix: IMPU_wlan to represent the selected result, and returns theINVITE request to the S-CSCF.

In Step 8, according to the selection of the DSF, the S-CSCF selects theregistration connection with the IMPU being the IMPU_wlan. In thisembodiment, it is assumed that only one registration connection, thatis, contact-2, exists, the S-CSCF fills the Request-URI with the contentof the contact-2, and then delivers the INVITE request. In this manner,the call is connected with the WLAN access network. If a plurality ofregistration connections performed with the IMPU_wlan, the S-CSCF maydeliver the call request to the connections at the same time or insequence, and performs the forking operation.

In Step 9, the multimode terminal receives the call under the WLAN andreturns the call final response.

Referring to FIG. 6, the system according to a first embodiment of thepresent invention includes a routing decision entity (may be, but notlimited to, the DSF, or another AS), a routing execution entity (may bethe S-CSCF), and a multimode terminal (may be the multimode terminal ofthe WCDMA, the multimode terminal of the CDMA2000, or other mobilemultimode terminals of other standards) connected in sequence.

The multimode terminal is adapted to notify an access network typeidentity corresponding to the current access mode to a network side witha registration signaling when registering.

The routing decision entity is adapted to select the access modeaccording to various policies, and instruct the routing execution entityto perform the call connection to a called party in the selection accessmode with the corresponding access network type identity.

The routing execution entity is adapted to perform the call connectionaccording to the instruction of the routing decision entity.

Referring to FIG. 7, the multimode terminal (that is, the multimodeterminal of the present invention) includes an access networkidentifying unit and an adding unit connected with each other. Theaccess network identifying unit is adapted to identify an adopted accessnetwork when the multimode terminal gets access to network. The addingunit is adapted to add the corresponding access network type identity tothe registration signaling transmitted to the network side according tothe current access network of the multimode terminal identified by theaccess network identifying unit, when the multimode terminal initiatesto register.

The routing decision entity (that is, the routing decision entity of thepresent invention) includes a saving unit and an instructing unitconnected to each other. The saving unit is adapted to save the accessnetwork type identity carried in the registration signaling (afteracquiring the access network type identity, the routing execution entitytransmits the access network type identity to the routing decisionentity), and provide the access network type identity to the instructingunit. The instructing unit is adapted to extract the correspondingaccess network type identity from the saving unit, after the routingdecision entity selects the access mode according to the policy, andcarry the extracted access network type identity in an instructionsignaling delivered to the routing execution entity.

To sum up, in the present invention, the reg-id is not adopted, andnumerals such as 1 and 2 do not serve as the value of the reg-id, butthe access network type identity is adapted to represent the access modeof the terminal. When registering, the terminal notifies the accessnetwork type identity to the network side. When performing the callconnection to the called party, the routing decision entity in thenetwork selects the access mode and instructs the routing executionentity to perform the call connection in the selected access mode withthe corresponding access network type identity.

Further, when registering, the network side identifies the multipleregistration events of the same terminal according to the acquiredaccess network type identity so as to hold the plurality of registrationconnections of the same terminal, thereby solving the problem that thesame terminal holds the plurality of registration connections at the IMSnetwork, and the problem that after selecting the access mode, therouting decision entity correspondingly instructs the routing executionentity to perform the call connection in the selected access mode.

Referring to FIG. 8, the method according to a fifth embodiment of thepresent invention includes the steps as follows.

In Step S201, when establishing a registration connection, the terminalnotifies a current access mode type and a resource name bound with thecurrent access mode type to the network side.

In the existing systems, when being called, for the case that aplurality of terminals share the IMPU, the GRUU concept is introduced tothe internet engineering task force (IETF) and the 3GPP in order toprevent the SIP REQUEST from being divided into a plurality of userequipments (UEs). The GRUU includes the resource names Instance_id ofthe IMPU and the UEs. The Instance_id is adapted to identify the ID ofthe UE Instance (that is, one terminal only has one Instance_id), and inthis manner, the GRUU may identify one UE. Even if the IMPU is shared bymultiple UEs, the GRUU serving as the REQUEST URI may still ensure thatthe SIP message is transmitted to the uniquely designated UE.

As the multimode terminal supporting various access modes is proposed,in the present invention, the different access mode types of the samemultimode terminal are considered as the different application examplesof the multimode terminal. The multimode terminal has a plurality ofaccess network modules, so in the present invention, the differentaccess modes of one multimode terminal respectively have thecorresponding Instance_id, that is, the instance_id is bound with theaccess mode type.

The current access mode type may be carried in a P-Access-Network-Infoheader field of the registration message (the P-Access-Network-Info is aheader field in the SIP protocol, and may be adapted to carry the accessnetwork information and the user position information) so as to benotified to the network side.

In Step S202, the network side distributes the GRUU to the terminalaccording to the resource name.

The GRUU includes the IMS public user identity IMPU and the instance_idnotified by the terminal.

In Step S203, the network side associates the access mode type notifiedby the terminal with the distributed GRUU.

In Step S204, when performing the call connection to the called party,the routing decision entity on the network side selects the access mode.

The related policy of selecting the access mode by the routing decisionentity includes at least one selected from among an operator policy,calling party preference information, access network capability, anaccess network status, a media class, a component in the media class,and attribute information of each component in the media class.

Before the routing decision entity selects the access mode, the methodfurther includes the following steps: The routing decision entity judgeswhether or not at least two types of media components exist in a callingsession message, and, if yes, the routing decision entity furtherselects whether or not to divide the calling session message into mediastreams according to the media components; (i.e., the routing decisionentity may further select whether to divide each divided media streaminto an uplink media stream and a downlink media stream), and, if stillyes, the routing decision entity selects the access mode correspondingto each media stream, and instructs the routing execution entity toconnect to the media stream using the GRUU corresponding to the selectedaccess mode. If less than two types of media components exist in acalling session message, the routing decision entity directly selectsthe access mode of the calling session message, and instructs therouting execution entity to perform the call connection with the GRUUcorresponding to the selected access mode.

In Step S205, the routing decision entity on the network side instructsthe routing execution entity to perform the call connection with theGRUU corresponding to the selected access mode.

In detail, the routing decision entity carries the GRUU associated withthe selected access mode type in the instruction message delivered tothe routing execution entity. The routing execution entity locates theregistration connection according to the GRUU carried in the instructionmessage, and performs the call connection based on the registrationconnection.

Referring to FIG. 9, the present invention further provides a routingdecision entity, which includes an associating unit, an access modeselection unit, and an instructing unit, and further includes aconfirming unit and a dividing unit.

The associating unit is adapted to associate the access mode typenotified by the multimode terminal with the GRUU distributed by therouting execution entity.

The confirming unit is adapted to transmit a trigger signal, whenconfirming that at least two types of media components exist in thereceived calling session message, and further confirming to divide thecalling session message into the media streams according to the mediacomponents.

The dividing unit is adapted to divide the calling session message intothe media streams according to the media components when receiving thetrigger signal transmitted from the confirming unit, and notify theaccess mode selection unit to respectively select the access modecorresponding to each media stream.

The access mode selection unit is adapted to select the access mode.

The instructing unit is adapted to respectively acquire the GRUUcorresponding to the access mode type selected by the access modeselection unit from the associating unit, and instruct the routingexecution entity to perform the call connection with the GRUU.

Referring to FIG. 10, the present invention further provides a multimodeterminal, which includes an identifying unit and an adding unit.

The identifying unit is adapted to identify the access mode type of themultimode terminal when establishing the registration connection.

The adding unit is adapted to add the current access mode type of themultimode terminal identified by the identifying unit and the resourcename bound with the current access mode type to the registration messagetransmitted to the network side.

The system according to a second embodiment of the present inventionincludes a multimode terminal, a routing execution entity, and a routingdecision entity.

The multimode terminal is adapted to notify the current access networktype and the resource name bound with the current access mode type tothe network side when establishing the registration connection.

The routing execution entity is adapted to serve as a registrationserver when the terminal establishes the registration connection,distribute a GRUU to the multimode terminal according to the resourcename notified by the multimode terminal, and perform the callconnection. The routing execution entity may be, for example, an S-CSCF.

The routing decision entity is adapted to associate the access mode typenotified by the multimode terminal with the GRUU distributed to themultimode terminal by the routing execution entity according to theresource name, select the access mode, and instruct the routingexecution entity to perform the call connection with the GRUUcorresponding to the selected access mode type. Practically, the routingdecision entity is a network element saving the related policy ofselecting the access mode, for example, the AS or a home subscriberserver (HSS).

The detailed description is given with two embodiments as follows.

In the method according to a sixth embodiment, when establishing theregistration connection, the terminal notifies the current access modetype and the instance_id bound with the current access mode type to thenetwork side. The network side associates the access mode type notifiedby the terminal with the distributed GRUU. The application serverconfirms that one type of media component exists in the calling sessionmessage, and it is not necessary to divide the media component. Then,when performing the call connection to the called party, the routingdecision entity selects the access mode for the calling session message.Finally, the routing decision entity instructs the routing executionentity to perform the call connection with the GRUU corresponding to theselected access mode type. Referring to FIG. 11, the method includes thesteps as follows.

In Step 1, the multimode terminal gets access to the IMS network fromthe WLAN and initiates a registration request REGISTER, a +sip.instanceparameter is added to a contact header field of the registrationrequest, and the content of the parameter is instance id_1 of themultimode terminal bound with the WLAN access mode. At the same time,the current access mode type information, that is, WLAN, is added to theP-Access-Network-Info header field of the registration request.

In Step 2, the S-CSCF generates GRUU_1 according to the IMPU and thevalue of the instance id_1 in the contact header field of theregistration request, carries the user registration event and the GRUU_1distributed to the terminal UE by the S-CSCF in the contact header fieldof the registration event notification message, and notifies theregistration event notification message to the application serverServer.

At the same time, the S-CSCF associates the contact_1 of theregistration request with the GRUU_1 distributed to the terminal UE.After receiving the registration event notification message, theapplication server Server acquires from the registration eventnotification message that the multimode terminal gets access to the IMSnetwork via the WLAN, and associates the WLAN access mode with theGRUU_1.

In Step 3, the multimode terminal gets access to the IMS network fromthe WCDMA and initiates another registration request, a +sip.instanceparameter is added to the contact header field of the registrationrequest, and the content of the parameter is instance id_2 of themultimode terminal bound with the WCDMA access mode. At the same time,the current access mode type information, that is, WCDMA, is added tothe P-Access-Network-Info header field of the registration request.

[Note]: After receiving the registration message, the S-CSCF acquiresthat this is a multiple registration event of the same terminalaccording to the different reg-ids (the reg-id is carried in the contactheader field of the registration request message, for the detailedcontent, please refer to the existing systems), and the originalcontact_1 connection (that is the contact established in Steps 1 and 2)is not deregistered.

Or, the S-CSCF judges that this is a multiple registration initiatedfrom the different access modes of the same terminal according to thedifferent instance IDs, so it is not necessary to adopt the reg-id.

In Step 4, the S-CSCF generates GRUU_2 according to the IMPU and thevalue of the instance id_2 in the contact header field of theregistration request, carries the user registration event and the GRUU_2distributed to the terminal UE by the S-CSCF in the contact header fieldof the registration event notification message, and notifies theregistration event notification message to the application serverServer.

At the same time, the S-CSCF associates the contact_2 of theregistration request with the GRUU_2 distributed to the terminal UE.After receiving the registration event notification message, theapplication server Server acquires from the registration eventnotification message that the multimode terminal gets access to the IMSnetwork from the WCDMA access, and associates the WCDMA access mode withthe GRUU_2.

In Step 5, when an incoming call is required to be connected to theterminal device of the called user, the call message INVITE is firstlytransmitted to the S-CSCF.

In Step 6, the S-CSCF triggers the INVITE to the application serverServer with the iFC.

In Step 7, the application server Server decides the terminal devicerequired to be connected to the call and the access mode (assumed to beWLAN) according to the related policy, and according to the associationrelation between the WLAN access mode and the GRUU_1, the Request-URIheader field content of the INVITE is filled with GRUU_1, and the INVITEwith the header field is returned to the S-CSCF.

In Step 8, the S-CSCF locates (selects) the registration connection ofthe GRUU_1 according to the selection of the application server Serverand the association relation between the contact_1 and the GRUU_1established in Steps 1 and 2, that is, the S-CSCF fills the Request-URIwith the contact content (that is, the contact_1) established in Steps 1and 2, and delivers the INVITE. In this manner, the call may beaccurately terminated at the specific access mode of the specificmultimode terminal device.

In Step 9, the multimode terminal receives the call under the WLAN mode,and returns the call final response.

In the method according to a seventh embodiment, when establishing theregistration connection, the terminal notifies the current access modetype and the instance_id bound with the current access mode type to thenetwork side. The network side associates the access mode type notifiedby the terminal with the distributed GRUU. The application serverconfirms that a plurality of types of media components exists in thecalling session message, and divides the session message according tothe media components based on a certain policy. Then, when performingthe call connection to the called party, the routing decision entityrespectively selects the access mode for each divided media stream.Finally, the routing decision entity instructs the routing executionentity to be connected to the media stream with the GRUU correspondingto the selected access mode. Referring to FIG. 12, the method includesthe steps as follows.

In Step 1, the multimode terminal gets access to the IMS network fromthe WLAN and initiates a registration request REGISTER, a +sip.instanceparameter is added to a contact header field of the registrationrequest, and the content of the parameter is instance id_1 of themultimode terminal bound with the WLAN access mode. At the same time,the current access mode type information, that is, WLAN, is added to theP-Access-Network-Info header field of the registration request.

In Step 2, the S-CSCF generates GRUU_1 according to the IMPU and thevalue of the instance id_1 in the contact header field of theregistration request, carries the user registration event and the GRUU_1distributed to the terminal UE by the S-CSCF in the contact header fieldof the registration event notification message, and notifies theregistration event notification message to the application serverServer.

At the same time, the S-CSCF associates the contact_1 of theregistration request with the GRUU_1 distributed to the terminal UE.After receiving the registration event notification message, theapplication server Server acquires from the registration eventnotification message that the multimode terminal gets access to the IMSnetwork from the WLAN access, and associates the WLAN access mode withthe GRUU_1.

In Step 3, the multimode terminal gets access to the IMS network fromthe WCDMA and initiates another registration request, a +sip.instanceparameter is added to the contact header field of the registrationrequest, and the content of the parameter is instance id_2 of themultimode terminal bound with the WCDMA access mode. At the same time,the current access mode type information, that is, WCDMA, is added tothe P-Access-Network-Info header field of the registration request.

[Note]: After receiving the registration message, the S-CSCF acquiresthat this is a multiple registration event of the same terminalaccording to the different reg-ids (the reg-id is carried in the contactheader field of the registration request message, for the detailedcontent, please refer to the existing systems), and the originalcontact_1 connection (that is the contact established in Steps 1 and 2)is not deregistered.

Or, the S-CSCF judges that this is a multiple registration initiatedfrom the different access modes of the same terminal according to thedifferent instance ids, so it is not necessary to adopt the reg-id.

In Step 4, the S-CSCF generates GRUU_2 according to the IMPU and thevalue of the instance id_2 in the contact header field of theregistration request, carries the user registration event and the GRUU_2distributed to the terminal UE by the S-CSCF in the contact header fieldof the registration event notification message, and notifies theregistration event notification message to the application serverServer.

At the same time, the S-CSCF associates the contact_2 of theregistration request with the GRUU_2 distributed to the terminal UE.After receiving the registration event notification message, theapplication server Server acquires from the registration eventnotification message that the multimode terminal gets access to the IMSnetwork from the WCDMA access, and associates the WCDMA access mode withthe GRUU_2.

In Step 5, when an incoming call is required to be connected to theterminal device of the called user, the call message INVITE is firstlytransmitted to the S-CSCF.

In Step 6, the S-CSCF triggers the INVITE to the application serverServer with the iFC.

In Step 7, the application server Server judges that a plurality oftypes of media components exists in the calling session message, anddivides the session message in term of the different media componentsaccording to the certain policy. The application server Server selectsthe terminal device and the access mode for each divided media streamaccording to the policy. In this embodiment, video and audio mediastreams are divided, it is decided that the video stream is connected tothe multimode terminal in the WLAN mode, and the audio flow is connectedto the multimode terminal in the WCDMA mode.

[Note]: the media stream may be further divided into the uplink and thedownlink media streams.

In Step 8 a, it is decided that the video stream is connected to themultimode terminal in the WLAN mode, according to the associationrelation between the WLAN access mode and the GRUU_1, the Request-URIheader field content of the INVITE is filled with the GRUU_1, and theINVITE with the header field is returned to the S-CSCF. The processproceeds to Step 9 a.

In Step 8 b, at the same time (with Step 8 a), it is decided that theaudio flow is connected to the multimode terminal in the WCDMA mode,according to the association relation between the WCDMA access mode andthe GRUU_2, the Request-URI header field content of the INVITE is filledwith the GRUU_2, and the INVITE with the header field is returned to theS-CSCF. The process proceeds to Step 9 b.

In Step 9 a, the S-CSCF locates (selects) the registration connection ofthe GRUU_1 according to the selection of the application server Serverand the association relation between the contact_1 and the GRUU_1established in Steps 1 and 2, that is, the S-CSCF fills the Request-URIwith the contact content (that is, the contact_1) established in Steps 1and 2, and delivers the INVITE. In this manner, the video media streammay be accurately terminated at the WLAN access mode of the specificmultimode terminal device. The process proceeds to Step 10 a.

In Step 9 b, at the same time (with Step 9 a), the S-CSCF locates(selects) the registration connection of the GRUU_2 according to theselection of the application server Server and the association relationbetween the contact_2 and the GRUU_2 established in Steps 3 and 4, thatis, the S-CSCF fills the Request-URI with the contact content (that is,the contact_2) established in Steps 3 and 4, and delivers the INVITE. Inthis manner, the audio media stream may be accurately terminated at theWCDMA access mode of the specific multimode terminal device. The processproceeds to Step 10 b.

In Step 10 a, the multimode terminal receives the video media streamunder the WLAN mode, and returns the call final response.

In Step 10 b, the multimode terminal receives the audio media streamunder the WCDMA mode, and returns the call final response.

In the method according to the sixth and the seventh embodiments, whenestablishing the registration connection, the terminal notifies thecurrent access mode type and the instance_id bound with the currentaccess mode type to the network side. The network side associates theaccess mode type notified by the terminal with the GRUU distributed tothe terminal according to the instance_id. Then, when performing thecall connection to the called party, the routing decision entityrespectively selects the access mode and instructs the routing executionentity to perform the call connection with the GRUU corresponding to theselected access mode. Therefore, with the series of operations, forexample, binding the instance_id with the current access mode type,distributing the GRUU according to the instance_id, and associating thecurrent access mode type with the GRUU, after selecting the access modeaccording to the certain policy, the routing decision entity mayinstruct the routing execution entity to perform the call connection inthe selected access mode.

Before the routing decision entity selects the access mode, the methodfurther includes the following steps: the routing decision entity judgeswhether at least two types of media components exist in the callingsession message or not, and, if yes, the routing decision entity furtherselects whether to divide the calling session message into the mediastreams according to the media components or not, if yes, the routingdecision entity respectively selects the access mode corresponding toeach media stream, and respectively instructs the routing executionentity to be connected to the media stream with the GRUU correspondingto the selected access mode. Otherwise, the routing decision entitydirectly selects the access mode of the calling session message, andinstructs the routing execution entity to perform the call connectionwith the GRUU corresponding to the selected access mode. In this manner,the media stream is connected with the most appropriate access network,thereby improving the network transferring efficiency, and improving theuser service experience.

Further, when judging to divide the calling session message into themedia streams according to the media components, the routing decisionentity divides each divided media stream into the uplink media streamand the downlink media stream so as to well utilize various accessnetworks, and improve the user service experience.

The method according to an eighth embodiment includes the steps asfollows: (1) when establishing the registration connection, the terminalnotifies the identification information of the current access mode typeto the network side; then, (2) when performing the call connection tothe called party, the routing decision entity on the network sidedivides the calling session message into the media streams according tothe media components (may further divide each media component into theuplink media stream and the downlink media stream), respectively selectsthe access mode corresponding to each media stream, and respectivelyinstructs the routing execution entity to be connected to the mediastream with the identification information corresponding to the selectedaccess mode.

The identification information of the access network type is the currentaccess mode type and the resource name instance_id bound with thecurrent access mode type, or the content (for example, the name isaccesstype, and the value may be “wlan” or “wcdma” etc.) carried in theadded parameter in the feature tag.

Further, in the present invention, the division may be directlyperformed without judging the number of the media components in thecalling session message. Alternatively, when it is confirmed that atleast two media components exist in the calling session message, thecalling session message is divided into the media streams according tothe media components.

Referring to FIG. 13, the present invention further provides a routingdecision entity, which includes a saving unit, a dividing unit, anaccess mode selection unit, and an instructing unit, and may furtherinclude a confirming unit.

The saving unit is adapted to save the identification information of thecurrent access network type notified by the terminal when establishingthe registration connection.

The confirming unit is adapted to transmit the trigger signal to thedividing unit when confirming that at least two types of the mediacomponents exist in the calling session message.

The dividing unit is adapted to divide the calling session message intothe media streams according to the media components and transmit adivided result. The dividing unit may wait for the judging unit totransmit the trigger signal and perform the division operation, and mayalso directly perform the division operation.

The access mode selection unit is adapted to respectively select theaccess mode corresponding to each media stream according to the dividedresult transmitted from the dividing unit.

The instructing unit is adapted to respectively acquire theidentification information corresponding to the access mode typeselected by the access mode selection unit for each media stream fromthe saving unit, and instruct the routing execution entity to beconnected to the media stream with the identification information.

The detailed description is given below with reference to twoembodiments as follows.

In the method according to a ninth embodiment, the application serverjudges that the plurality of media components exists in the callingsession message, and decides to divide the session message according tothe media components based on the certain policy.

In this embodiment, a feature tag is added to identify the accessnetwork type, it is assumed that the name of the added feature tag isaccesstype, and the value is “wlan” or “wcdma” etc., for identifying thevarious different access modes.

Referring to FIG. 14, the method includes the steps as follows.

In Step 1, the multimode terminal gets access to the IMS network fromthe WLAN and initiates a registration request REGISTER, a contact-1address is carried in the request message, the accesstype parameteridentifying the access network type is carried after the contact headerfield, the value of the parameter is wlan, representing that themultimode terminal gets access to the IMS network from the WLAN network.After being forwarded with the corresponding entity, the request messagereaches the S-CSCF (the process is irrelevant to the present invention,so it is omitted here).

In Step 2, after finishing the user registration flow, the S-CSCFnotifies the user registration event and the contact header fieldcontent to the application server Server, and the contact header fieldcontent includes the accesstype parameter identifying the access networktype, and the value is wlan (the server has subscribed the userregistration event from the S-CSCF before, so here the S-CSCF may notifythe server, and the subscription process is irrelevant to the presentinvention, so it is omitted here).

In Step 3, the multimode terminal gets access to the IMS network fromthe WCDMA and initiates another registration request, the contact_2address and the accesstype parameter with the value being wcdma arecarried in the request message, representing that the multimode terminalgets access to the IMS network from the WCDMA network.

[Note]: After receiving the registration message, the S-CSCF acquiresthat this is a multiple registration event of the same terminalaccording to the different reg-ids (the reg-id is carried in the contactheader field of the registration request message), and the originalcontact_1 connection is not deregistered.

In addition, as an added method, the S-CSCF judges that this is amultiple registration initiated from the different access modes of thesame terminal according to the different accesstype.

In Step 4, the S-CSCF also notifies the new registration event of theuser and the contact header field content to the application serverServer, and the contact header field content includes the accesstypeparameter identifying the access network type, and the value is wcdma.

In Step 5, when one call is required to be connected to the user, thecall signaling INVITE is firstly transmitted to the S-CSCF.

In Step 6, the S-CSCF triggers the call signaling to the applicationserver Server with the iFC.

In Step 7, the application server Server judges that a plurality oftypes of media components exists in the calling session message, anddivides the session message according to the different media componentsbased on the certain policy. The application server Server selects theterminal device and the access mode for each divided media streamaccording to the policy. In this embodiment, video and audio mediastreams are divided, it is decided that the video stream is connected tothe multimode terminal in the WLAN mode, and the audio flow is connectedto the multimode terminal in the WCDMA mode.

[Note]: the media stream may be further divided into the uplink and thedownlink media streams.

In Step 8 a, it is decided that the video stream is connected to themultimode terminal in the WLAN mode, the Accept-Contact header fieldcontent is filled with accesstype=wlan, and the INVITE with the headerfield is returned to the S-CSCF.

In Step 8 b, at the same time, it is decided that the audio flow isconnected to the multimode terminal in the WCDMA mod, the Accept-Contactheader field content is filled with accesstype=wcdma, and the INVITEwith the header field is returned to the S-CSCF.

In Step 9 a, the S-CSCF locates (selects) the registration connection ofaccesstype=wlan according to the selection of the application serverServer, that is, the S-CSCF fills the Request-URI with the contact_1content, and delivers the INVITE. In this manner, the video media streammay be accurately terminated at the WLAN access mode of the specificmultimode terminal device.

In Step 9 b, the S-CSCF locates (selects) the registration connection ofaccesstype=wcdma according to the selection of the application serverServer, that is, the S-CSCF fills the Request-URI with the contact_2content, and delivers the INVITE. In this manner, the audio media streammay be accurately terminated at the WCDMA access mode of the specificmultimode terminal device.

In Step 10 a, the multimode terminal receives the video media streamunder the WLAN mode, and returns the call final response.

In Step 10 b, the multimode terminal receives the audio media streamunder the WCDMA mode, and returns the call final response.

In the method according to a tenth embodiment, when establishing theregistration connection, the terminal notifies the current access modetype and the instance_id bound with the current access mode type to thenetwork side. The network side associates the access mode type notifiedby the terminal with the distributed GRUU. The application serverconfirms that a plurality of types of media components exists in thecalling session message, and divides the session message according tothe media components based on the certain policy. Then, when performingthe call connection to the called party, the routing decision entityrespectively selects the access mode for each divided media stream.Finally, the routing decision entity instructs the routing executionentity to be connected to the media stream with the GRUU correspondingto the selected access mode.

To sum up, the method according to the ninth and the tenth embodimentsof the present invention, when establishing the registration connection,the terminal notifies the identification information of the currentaccess network type to the network side. When performing the callconnection to the called party, the routing decision entity on thenetwork side divides the calling session message into the media streamsaccording to the media components, respectively selects the access modecorresponding to each media stream according to the related policy, andrespectively instructs the routing execution entity to be connected tothe media stream with the identification information corresponding tothe selected access mode. In this manner, the media stream is connectedwith the most appropriate access network, thereby improving the networktransferring efficiency, and improving the user service experience.

Further, when judging that it is necessary to divide the calling sessionmessage into the media streams according to the media components, therouting decision entity divides each divided media stream into theuplink media stream and the downlink media stream so as to well utilizethe various access networks, and improve the user service experience.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the scope or spirit of the invention. Forexample, in addition to being applied to the multimode terminal of theWCDMA in the embodiments, the present invention may also be applied tothe multimode terminal of the CDMA2000 and the mobile multimodeterminals of other standards. In view of the foregoing, it is intendedthat the present invention cover modifications and variations of thisinvention provided that they fall within the scope of the followingclaims and their equivalents.

What is claimed is:
 1. A method for providing an access networkselection to a multimode terminal, comprising: obtaining, by a routingdecision entity in an internet protocol (IP) multimedia sub-system(IMS), a plurality of access network type identities sent by themultimode terminal when the multimode terminal registers to the IMSthrough a plurality of access networks corresponding to the plurality ofaccess network type identities, wherein each of the plurality of accessnetwork type identities sent by the multimode terminal is carried in acontact header filed in a registration message; receiving, by therouting decision entity, an INVITE message which is sent by a ServingCall Session Control Function (S-CSCF) in the IMS; after receiving theINVITE message, creating, by the routing decision entity, an INVITEmessage in which an Accept-Contact header field carries one of theplurality of the access network type identities; and sending, by therouting decision entity, the created INVITE message to the S-CSCF sothat the S-CSCF communicates with the multimode terminal through anaccess network corresponding to the access network type identity carriedin the Accept-Contact header field.
 2. A routing decision entity in aninternet protocol (IP) multimedia sub-system (IMS), comprising: areceiver configured to obtain a plurality of access network typeidentities sent by a multimode terminal when the multimode terminalregisters to the IMS through a plurality of access networkscorresponding to the plurality of access network type identities,wherein each of the plurality of access network type identities sent bythe multimode terminal is carried in a contact header filed in aregistration message; receive an INVITE message which is sent by aServing Call Session Control Function (S-CSCF) in the IMS; and create anINVITE message in which an Accept-Contact header field carries one ofthe plurality of the access network type identities; and a transmitterconfigured to send the created INVITE message to the S-CSCF so that theS-CSCF communicates with the multimode terminal through an accessnetwork corresponding to the access network type identity carried in theAccept-Contact header field.
 3. A system for providing an access networkselection to a multimode terminal, comprising: a routing decisionentity, configured to obtain a plurality of access network typeidentities sent by the multimode terminal when the multimode terminalregisters to the IMS through a plurality of access networkscorresponding to the plurality of access network type identities,wherein each of the plurality of access network type identities sent bythe multimode terminal is carried in a contact header filed in aregistration message; receive an INVITE message which is sent by aServing Call Session Control Function (S-CSCF) in the IMS; create, afterreceiving the INVITE message, an INVITE message in which anAccept-Contact header field carries one of the plurality of the accessnetwork type identities; and send the created INVITE message to theS-CSCF so that the S-CSCF communicates with the multimode terminalthrough an access network corresponding to the access network typeidentity carried in the Accept-Contact header field; and the S-CSCF,configured to communicate with the multimode terminal through the accessnetwork corresponding to the access network type identity carried in theAccept-Contact header field.